This invention relates to a hollow fiber and tubesheet assembly wherein the hollow fiber is a water wet fiber and a novel tubesheet material. In another aspect, this invention relates to a method for preparing such a tubesheet assembly.
The hollow fiber tubesheet assemblies of this invention are major components of hollow fiber membrane devices. Many types of hollow fibers are prepared by a wet spinning process, one such class of fibers are the cellulose ester fibers. Hollow fiber membrane devices of cellulose ester hollow fibers are useful in the purification of water and in the separation of gases. An example of cellulose ester hollow fibers by a wet spinning process is described U.S. Pat. No. 3,532,527 (incorporated herein by reference), in which a mixture of a cellulose ester, a plasticizer for the cellulose ester, and a polyol is melt extruded using a suitable extruder to prepare a hollow fiber. The fiber is passed through an air zone wherein the fiber is quenched to freeze the molten mixture, thereafter the fiber is passed through a water bath wherein the plasticizer and polyol are leached out and replaced by water. As the fiber exits the water bath, the fiber is covered with droplets of water and the surface is water saturated. To make hollow fiber devices from such fibers, it is necessary to form tubesheets of a thermoset or thermoplastic material about a portion of the hollow fibers. Similar processes are used for other classes of hollow fibers.
One significant problem in forming tubesheets about a water wet hollow fiber is that most thermoset and thermoplastic materials do not adhere to wet fibers. Therefore, in order to form tubesheets about the water wet hollow fibers, it is highly desirable to dry a portion of the hollow fibers so that the tubesheets may be formed about them. Failure to dry the fibers results in a tubesheet which will not adhere or will adhere poorly to the fibers. One problem with drying the fibers is that if the fibers are dried too much the efficacy of such fibers for certain operations will be significantly diminished. What is needed is a tubesheet assembly and method for formation of a tubesheet assembly, which can be formed from water wet hollow fibers.